The long-term objective of this research is to gain an understanding of the inherited control mechanisms which regulate immunoglobulin gene expression. Heteroclytic anti-NP antibody has been thought to be the product of the VHNP-b gene. Balb/c mice which do not express the b allele at the Igh complex normally do not synthesize heteroclytic anti-NP antibody. We recently found that under some experimental conditions Balb/c B cells could be triggered to produce heteroclytic anti-NP. On this basis, we plan to study production of heteroclytic anti-NP antibody in Balb/c mice as an example of inappropriate VH gene expression. A major goal of the proposed research is to characterize the population of Lambda+ heteroclytic anti-NP antibodies synthesized by Balb/c mice. Monoclonal anti-NP antibodies will be utilized to examine the extent of diversity within this population. A serological approach will be employed to evaluate the possible relationship between Balb/c Lambda+ heteroclytic anti-NP antibodies and NP-b id+ antibody molecules. Experiments outlined in this proposal are also directed towards analyzing the activities of T cells in regulating expression of this hidden idiotype(s). The role(s) of Ly 1 helper and/or Ly 23 suppressor T cells in limiting production of Lamda+ heteroclytic anti-NP antibodies in Balb/c mice will be described. This work will hopefully provide new insight into the basis of inherited idiotypic expression.